1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a flexible jogger for a signature feeder in a printing press.
2. Background Information
During printing press operations printed signatures are feed to downstream processes. Signature feeders are used to collect and align (register) the signatures for controlled feeding to a subsequent operation. Mechanical jogging devices have been used for loading signatures into a hopper, or feeder pocket, of a signature feeder to xe2x80x9cjog,xe2x80x9d or move the signatures into alignment, as they are come into the hopper, thereby improving signature registration. Existing mechanical joggers push incoming signatures against a backstop plate in a hopper, thereby registering the signatures as they form a stack in the hopper.
Existing mechanical joggers do not adjust to signature stack height or to signature characteristics.
An object of the present invention is to provide a signature feeder having a jogger which automatically adjusts to signature stack height and to signature characteristics so as to improve signature registration.
The present invention provides a jogger for a signature feeder having a hopper for receiving signatures at an upper end of the hopper and forming a stack of the signatures in a vertical direction starting at a lower end of the hopper, the jogger comprising: a back stop disposed at a first side of the hopper; and a flexible jogging element disposed at a second side of the hopper opposite the first side, the flexible jogging element being oscillated in a direction lateral to the vertical direction so as to periodically bend the flexible jogging element against the stack of the signatures and form a pushing zone and a vibrating zone below the pushing zone in the hopper, the signatures in the pushing zone being urged against the back stop by the flexible jogging element so as to register the signatures as the stack is formed, the signatures in the vibrating zone being vibrated by the flexible jogging element so as to improve the registration of the signatures in the stack.
The respective vertical length of each of the pushing zone and the vibrating zone is a function of the height of the stack
The flexible jogging element bends toward the stack of signatures so as to assume a curved shape, the curved shape being a function of at least one of the height of the stack of signatures and a characteristic of the signatures, such as a modulus of a material of the signatures, a stiffness of the signatures, a size of the signatures and a shape of the signatures.
The curved shape that the flexible jogging element assumes may be parabolic. The flexible jogging element may be non-translatably and non-rotatably fixed at a lower end of the hopper. The flexible jogging element may be pivotably fixed at a lower end of the hopper.
The flexible jogging element may be oscillated at a portion of the element disposed at an upper end of the hopper.
The flexible jogging element maybe a thin plate. The flexible jogging element may include a plurality of adjacent fingers.
The flexible jogging element may be made of metal or of a plastic material.
The flexible jogging element is oscillated using at least one of a cam and a crank arm.
The back stop may be rigid or flexible, and may be curved. The back stop may have a motion imparted to it.
The present invention also provides a method for jogging signatures in a signature feeder, the method comprising: receiving the signatures at an upper end of a hopper of the signature feeder and forming a stack of the signatures in a vertical direction starting at a lower end of the hopper; and oscillating a flexible jogging element in a direction lateral to the vertical direction so as to periodically bend the flexible jogging element against the stack of the signatures and form a pushing zone and a vibrating zone below the pushing zone in the hopper, the flexible jogging element being disposed at a first side of the hopper, the signatures in the pushing zone being urged by the flexible jogging element against a back stop disposed at a second side of the hopper opposite the first side so as to register the signatures as the stack is formed, the signatures in the vibrating zone being vibrated by the flexible jogging element so as to improve the register of the signatures in the stack.